1,721,002 research outputs found
Optimized co-production of lipids and carotenoids from Ettlia sp. by regulating stress conditions
No full textThis study used a single strain Ettlia sp. YC001 and two stages to optimize the production of three materials: lipids, lutein, and β-carotene. In the cultivation stage for lutein production, different temperatures, light qualities, and intensities were applied. The highest biomass was obtained at 35 °C, but the maximum lutein productivity of 6.1 mg/L/d achieved at 25 °C. In the stress stage for lipids and β-carotene production, UV-A and nitrogen starvation were applied. While UV stress increased the chlorophyll-a and β-carotene content. The β-carotene, oleic acid, and lipids significantly increased under nitrogen starvation with a high light intensity of 1200 μmol/m2/s, plus the Ettlia sp. changed from green to red. The results showed that Ettlia sp. can be an effective microalga for the co-production of lutein, β-carotene, and biodiesel
A novel microcystin-degrading bacterium, microbacterium sp. MA21
No full textA microcystin-degrading bacterium was isolated from Daechung reservoir, Korea. Theisolated bacterium was identified as Microbacterium sp. by 16S rRNA gene sequence analysis, anddesignated as Microbacterium sp. MA21. This strain degraded cyanobacterial hepatotoxin, microcystin-LR, over 80% when incubated at 30℃ for 12 hr in R2A medium. Two unknown metabolitesof microcystin were also identified during the degradation process. Although only Sphinogomonasand Actinobacteria have been known to degrade microcystin previously, this is the first report thatMicrobacterium sp. MA21 could degrade microcystin.open
Dynamics of bacterial communities analyzed by DGGE during cyanobacterial bloom in Daechung Reservoir, Korea
No full textThe change of microbial communities during cyanobacterial bloom was comparatively analyzed by 16S rDNA PCR-DGGE in Daechung Reservoir during 2003~2005. Morphological analysis showed that Cyanophyceae dominated algal community in the bloom. Dominant cyanobacteria were Microcystis, Planktothrix (Oscillatoria), Phormidium and Anabaena. We used 16S rDNA-denaturing gradient gel electrophoresis (DGGE) profiles and phylogenetic affiliations of the DGGE bands to analyze the community structure and diversity of the predominant microbial
community. The DGGE band patterns demonstrated that the most frequent bands were identified as Microcystis during the monitoring periods, Planktothrix also dominated on September 2003 and 2004, whereas Anabaena was showed a peak on September 2005 and Aphanizomenon on August 2003. DGGE and phylogenetic analysis provided us new information that could not be obtained by traditional, morphological analysis. The relationship between cyanobacteria and other aquatic bacteria can be traced and their genetic diversity also identified in detail.open
Effects of photoperiod on nutrient removal, biomass production, and algal-bacterial population dynamics in lab-scale photobioreactors treating municipal wastewater
No full textEffects of photoperiod were investigated in lab-scale photobioreactors containing algal-bacterial consortia to reduce organic nutrients from municipal wastewater. Under three photoperiod conditions (12h:12h, 36h:12h, and 60h:12h dark-light cycles), nutrient removals and biomass productions were measured along with monitoring microbial population dynamics. After a batch operation for 12 days, 59-80% carbon, 35-88% nitrogen, and 43-89% phosphorus were removed from influents, respectively. In this study, carbon removal was related positively to the length of dark cycles, while nitrogen and phosphorus removals inversely. On the contrast, the highest microbial biomass in terms of chlorophyll a, dry cell weight, and algal/bacterial rRNA gene markers was produced under the 12h:12h dark-light cycle among the three photoperiods. The results showed 1) simultaneous growths between algae and bacteria in the microbial consortia and 2) efficient nitrogen and phosphorus removals along with high microbial biomass production under prolonged light conditions. Statistical analyses indicated that carbon removal was significantly related to the ratio of bacteria to algae in the microbial consortia along with prolonged dark conditions (p<0.05). In addition, the ratio of nitrogen removal to phosphorus removal decreased significantly under prolonged dark conditions (p<0.001). These results indicated that the photoperiod condition has remarkable impacts on adjusting nutrient removal, producing microbial biomass, and altering algal-bacterial population dynamics. Therefore, the control of photoperiod was suggested as an important operating parameter in the algal wastewater treatment.open
Asprobacter aquaticus gen. nov., sp. nov., a prosthecate alphaproteobacterium isolated from fresh water
No full textA novel Gram-negative bacterium strain, DRW22-8T, was isolated from fresh water taken at a depth of 22 m at Daechung Reservoir, Republic of Korea. The cells of strain DRW22-8T were aerobic and motile with a single polar flagellum or nonmotile (stalked), and formed creamy-white colonies on R2A agar. The phylogenetic analysis based on 16S rRNA gene sequencing indicated that the strain formed a separate lineage within the order Rhodobacterales, showing similarity values under 91.8% with its closest phylogenetic neighbours, Hirschia litorea, Hirschia baltica and Hirschia maritima. The chemotaxonomic results showed Q-10 as the predominant respiratory ubiquinone, three unidentified glycolipids, an unidentified lipid and phosphatidylglycerol as the major polar lipids, and C16: 0, 11-methyl C18: 1, C18: 1 ω7c and/or C18: 1 ω6c as the major fatty acids. The DNA G+C content was 64.4 mol%. The combined genotypic and phenotypic data showed that strain DRW22-8T could be distinguished from all genera within the family Hyphomonadaceae and represented a novel genus, Asprobacter gen. nov., with the name Asprobacter aquaticus sp. nov., in the family Hyphomonadaceae. The type strain is DRW22-8T (=KCTC 42356T=JCM 30469T).
Raceway cultivation of Spirulina platensis using underground water
No full textThe semi-outdoor cultivation of Spirulina platensis was attempted using an underground-water-based medium. Occurrence of contaminant organisms such as Chlorella sp. and Chlamydomonas sp. was not found from a microscopic observation and bacteria were not detected from denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rDNA during the cultivation, owing to pH control and the high quality of the underground water. The mean productivity was high at 10.5 g/m2/d with a range of 4.2-12.3 g/m2/d despite the unfavorable weather conditions of the rainy season. The cultivated S. platensis included a normal protein content of 58.9%. Consequently, the underground water improved the biomass productivity and the biomass quality because of an abundant supplementation of natural minerals and through a contaminant-free culture.open
Rhizobacter profundi sp. nov., isolated from freshwater sediment
No full textThree bacterial strains, designated DS48-6-5T, DS48-6-7 and DS48-6-9, were isolated from a sediment sample taken from Daechung Reservoir (Republic of Korea) at a water depth of 48 m. Cells of the strains were Gram-stain-negative, aerobic, rod-shaped and motile with a single polar flagellum. Comparative 16S rRNA gene sequence studies showed that the three isolates had clear affiliation with Betaproteobacteria and the closest relatives were Rhizobacter bergeniae KCTC 32299T, Rhizobacter dauci DSM 11587T and Rhizobacter fulvus KCTC 12591T with 97.2-97.9% 16S rRNA gene sequence similarities; the 16S rRNA gene sequence similarities between the three strains were 99.5-100%. The only isoprenoid quinone of the three strains was ubiquinone-8, and the major fatty acids were summed feature 3 (C16: 1ω6c and/or C16: 1ω7c) and C16: 0. The G+C content of the genomic DNA of strains DS48-6-5T, DS48-6-7 and DS48-6-9 was 66.7, 67.0 and 66.8 mol%, respectively. DNA-DNA hybridization values of the novel strains with R. bergeniae KCTC 32299T, R. dauci DSM 11587T and R. fulvus KCTC 12591T were 19.3-48.5%. Based on the evidence from this taxonomic study using a polyphasic approach, it is proposed that strains, DS48-6-5T, DS48-6-7 and DS48-6-9, represent a novel species of the genus Rhizobacter, for which the name Rhizobacter profundi sp. nov. is proposed. The type strain is DS48-6-5T (=KCTC 42645T=NBRC 111169T).open
Jatrophihabitans fulvus sp. nov., an actinobacterium isolated from grass soil
No full textA Gram-stain-positive, aerobic, non-motile, non-spore-forming, rod-shaped bacterium, designated strain PB158T, was isolated from grass soil sampled in Daejeon, Republic of Korea. Comparative 16S rRNA gene sequence studies placed the novel isolate in the class Actinobacteria, and most closely related to Jatrophihabitans endophyticus S9-650T and Jatrophihabitans soli KIS75-12T with 98.1 and 97.0% 16S rRNA gene sequence similarity, respectively. Cells of strain PB158T formed yellow colonies on R2A agar, contained MK-9(H4) as the predominant menaquinone, meso-diaminopimelic acid as the diagnostic diamino acid, and included iso-C16: 0, C18: 1ω9c, and C17: 1ω8c as the major fatty acids (> 5%). The acyl type was found to be N-glycolylated. The G+C content of genomic DNA of strain PB158T was 72.4 mol%. In DNA？DNA hybridizations, the DNA？DNA relatedness value observed between strain PB158T and the type strain of J. endophyticus was 21.8% indicating that the two strains do not belong to the same species. Thus, the combined genotypic and phenotypic data supported the conclusion that strain PB158T represents a novel species of the genus Jatrophihabitans, for which the name Jatrophihabitans fulvus sp. nov. is proposed. The type strain is PB158T (=KCTC 33605T=JCM 30448T).open
Microcystin biosynthesis and mcyA expression in geographically distinct Microcystis strains under different nitrogen, phosphorus and boron regimes
No full textRoles of nutrients and other environmental variables in development of cyanobacterial bloom and its toxicity are complex and not well understood. We have monitored the photoautotrophic growth, total microcystin concentration, and microcystins synthetase gene (mcyA) expression in lab-grown strains of Microcystis NIES 843 (reference strain), KW (Wangsong Reservoir, South Korea), and Durgakund (Varanasi, India) under different nutrient regimes (nitrogen, phosphorus, and boron). Higher level of nitrogen and boron resulted in increased growth (avg. 5 and 6.5 Chl a mg/L, resp.), total microcystin concentrations (avg. 1.185 and 7.153 mg/L, resp.), and mcyA transcript but its expression was not directly correlated with total microcystin concentrations in the target strains. Interestingly, Durgakund strain had much lower microcystin content and lacked microcystin-YR variant over NIES 843 and KW. It is inferred that microcystin concentration and its variants are strain specific. We have also examined the heterotrophic bacteria associated with cyanobacterial bloom in Durgakund Pond and Wangsong Reservoir which were found to be enriched in Alpha-, Beta-, and Gammaproteobacteria and that could influence the bloom dynamics.open
Change of phytoplankton community by ultrasonication in eutrophic ponds
No full textThe effects of ultrasonication on phytoplankton were investigated in two ponds in which physicochemical and biological water quality was similar, one as a treatment and the other as a control. The samples were collected from August 18 to September 30 in 2open
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